/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.vm.opcode;

import axil.api.AxilObject;
import axil.api.extend.Environment;
import axil.api.extend.Parameters;
import axil.api.extend.Source;
import axil.engine.access.AccessPath;
import axil.vm.stack.StackFrame;

import static axil.framework.Functions.debug;
import static axil.framework.Functions.empty;


/**
 * An opcode that represents accessing host application objects via an access
 * path, but where the root is not in the context, the root is a temporary scoped
 * value. For example:
 *
 * 		inject(carts,items, 0.00, func(total, item, total + item.price))
 *
 * In this example, "item.price" is the access path, but the value of "item"
 * comes from the stack, not the context.
 */
public class OpStackPath extends Opcode {
	private int id;
	private AccessPath path;


	public OpStackPath(Source source, int id, String ident) {
		super(source);
		assert id > 0;
		assert ! empty(ident);
		this.id = id;
		this.path = new AccessPath(ident.split("\\."));
	}


	/**
	 * Relink this instruction, replacing the bad variable ID with the good
	 * variable ID. This is used when linking code that contains forward
	 * references, allowing us to compile in a single pass, but correct later.
	 */
	public void relink(int bad, int good) {
		if (id == bad) {
			id = good;
		}
	}


	/**
	 * Dump the content of this node to the diagnostic device. This is strictly
	 * for internal diagnostics, not for application use.
	 */
	public void dump(int indent) {
		debug(indent, "STACK(path) " + id + ", " + path.toString());
	}


	/**
	 * Evaluate this object in the given context and environment. A non-null
	 * object must be returned.
	 */
	protected AxilObject evaluate(Environment env, Parameters params) {
		return path.eval(((StackFrame)params).id(id));
	}
}
